Gastro-retentive drug delivery system

ABSTRACT

The invention relates to floating drug delivery systems (FDDS) that provide solutions to the particular problems often encountered with floating drug delivery systems described in the art. On such generally recognized problem is the vulnerability of the systems, especially damage to the gas-filled compartment making it accessible to water so as to impair its buoyancy, ultimately resulting in insufficient gastric residence time. The invention, in an aspect, provides a self-repairing FDDS that maintains its floating capacity after damaging. The floating drug delivery systems of the invention, furthermore, allow for incorporation of high loads of active ingredients. The floating drug delivery systems can be designed in such a way that release of active ingredient from the system occurs entirely independent from the pH of the fluid surrounding the system. Furthermore, the procedure of manufacturing the floating drug delivery system of the invention is simple and straightforward, and therefore economically attractive.

FIELD OF THE INVENTION

The invention relates to the fields of pharmacy and medicine. Amongothers, it relates to oral gastro-retentive drug delivery systems, inparticular floating drug delivery systems, and the uses thereof intherapy.

BACKGROUND OF THE INVENTION

Oral administration of drugs is the most preferable way of drug deliverydue to the simple and comfortable use and flexibility regarding dosestrength and type of formulation. These factors may increase patientcompliance. More than 50% of commercial drugs available in the marketuse oral administration for the delivery. During the last five decades,numerous oral delivery systems have been developed to act as a drugreservoir from which the active substance is released over an extendedperiod of time and at controlled rate of release. However, there isevidence that in vivo drug release of solid oral controlled releaseddosage form is unpredictable despite its excellent in vitro releaseprofile (Welling, P G 1993). Moreover, drug absorption profiles areoften unsatisfactory in relation to the desired plasma profile andhighly variable among individuals. One of the reasons for theunpredictable drug release, which causes variation in drug absorptionamong volunteers and patients, is associated with the transit time ofthe dosage form in the gastrointestinal tract (GIT). Gastric residencetime (GRT) appears to be a major cause of overall transit timevariability. First of all, the release of a drug from the deliverysystem may vary with the location of the drug in the GI-tract. If, forexample, the drug release is pH dependent, significant differences inthe release rate in the stomach and in the small intestine may exist.Secondly, the absorption of a drug may occur only in a limited part ofthe GI-tract. Once this part of the GI-tract is passed by the drugdosage form, drug release may occur in a reduced absorption or noabsorption at all any longer. Since many drugs are absorbed in theproximal site of small intestine, GRT is an important variable thataffects to a large extent oral drug absorption of controlled releasedosage form. For drugs that are absorbed only in a limited part of theGI-tract, the limited residence time in the stomach and the upper smallintestine, results in low oral bioavailability.

One of the options to reduce the variability in drug release and drugabsorption and to increase the bioavailability of drugs from orallyadministered drug delivery systems, especially controlled release drugdelivery systems, is to prolong the residence time of the dosage from inthe stomach. Delivery systems that are intended for this purpose areoften described as gastro-retentive dosage forms. Gastro-retentivedosage forms are delivery systems that will provide the system to beable to control the gastric residence time or gastric transit time ofthe dosage form to achieve a prolonged and predictable drug deliveryprofile in the upper part of the GI-tract. Controlling the residencetime of drug delivery system in the stomach will control the overallgastrointestinal transit time since GRT appears to be the major causesof overall transit time variability, thereby resulting in an improvedbioavailability of the drug.

The main objective in the development of gastro-retentive dosage formsis to overcome the clearance of gastric content that under normalcircumstances occurs within 1-2 hours in the fasted stated by thehousekeeping wave. Over the past three decades, the pursuit andexploration of devices designed to be retained in the upper part of thegastrointestinal (GI) tract has advanced consistently in terms oftechnology and diversity. Gastric retention will provide advantages suchas the delivery of drugs with a limited absorption window to those partsof the intestinal tract where absorption (with a slow release profile).Also, a longer residence time in the stomach could be advantageous forlocal action in the stomach or the upper part of the small intestine,for example treatment of peptic ulcer disease, or eradication ofHelicobacter pylori. Furthermore, improved bioavailability is expectedfor drugs that are absorbed preferentially from the upper part of theGI-tract such as the duodenum. These drugs can be delivered ideally byslow release from the stomach. Many drugs categorised as once-a-daydelivery have been demonstrated to have suboptimal absorption due todependence on the gastro-intestinal transit time of the dosage form,making traditional extended release development challenging. Therefore,a system designed for longer gastric retention will extend the timeduring which drug absorption can occur in for example the upper smallintestine.

Various approaches have been followed to encourage gastric retention ofan oral dosage form. Floating systems have low bulk density so that theycan float on the gastric juice in the stomach. For reviews on floatingdrug delivery systems, see Singh et al. (2000; J. Contr. Rel. 63,235-259) and Arora et al. (2005, AAPS PharmSciTech; 6(3) E372-E390) andreferences cited therein. Briefly, gastro-retentive systems can be basedon the following concepts:

A) buoyant (floating) systems: these are systems that have a densitylower that that of the gastric fluids so that they remain floating inthe stomach. These systems can be subdivided in:

-   -   A1) low-density systems have a density lower than that of the        gastric fluid so they are buoyant;    -   A2) hydrodynamically balanced systems (HBS)—incorporated buoyant        materials enable the device to float;    -   A3) effervescent systems—gas-generating materials such as        carbonates are incorporated. These materials react with gastric        acid and produce carbon dioxide (gas), which allows them to        float; The system contains means, such as a coating, to keep the        gas for some time in the delivery system.    -   A4) raft systems incorporate gels such as alginate or HPMC        gels—these have a carbonate component and, upon reaction with        gastric acid, bubbles form in the gel, enabling floating;        B) bioadhesive or mucoadhesive systems—these systems permit a        given drug delivery system to be incorporated with        bio/mucoadhesive agents, enabling the device to adhere to the        stomach (or other GI) walls, thus resisting gastric emptying.        C) systems that have a size or will expand in the stomach to a        size that is too large to pass the pyloric sphincter.

A number of major drug companies have focused efforts on the design ofgastric retention technologies. For instance, Alza Corporation hasdeveloped a gastro-retentive platform for the OROS® system, which showedprolonged gastric residence time in a dog model as the product remainedin the canine stomach at 12 hours post dose and was frequently presentat 24 hours. In humans, in the fasted state, the average gastricresidence time for the same system was 33 minutes. DepoMed, Inc. hasdeveloped technology that consists of a swellable tablet. Afteringestion of the tablet, it swells and achieves sufficient size toresist gastric emptying, while simultaneously providing controlledrelease of the drug. Two of the products that DepoMed is developinginclude Metformin GR™ and Ciprofloxacin GR™. Pfizer Pharmaceuticals haspatents for gastric retention technology that uses extendable arms.Merck & Co., Inc., has patents describing technologies using variousunfolding shapes to encourage gastric retention. Madopar® is an HBSfloating system containing 200 mg levodopa and 50 mg benserazide. Theformulation consists of a capsule designed to float on the stomachcontents. Following dissolution of the gelatin shell, a matrix body isformed consisting of the active drug and other substances.

A major disadvantage of many of the systems described above is that theyrequire special production technologies and/or specific machinery. Forexample, tabletting machines able to produce multi-layer tablets arenecessary to produce swellable multi-layer tablets. A floating systempatented by Eisa Co. Ltd. had the problem of incorporating the drug (seeSingh et al. (2000; J. Contr. Rel. 63, 235-259). The production ofsystems using effervescence has limitations regarding the use of aqueousliquids and the systems containing effervescence couples require special(e.g. moisture protecting) packaging. The production of systems with aspecial shape requires special compaction or moulding tools. Manysystems may suffer from limitations in dose strength; swellable systemsmay for example require large fractions of polymers in the system. Manyof the excipients (such as the polymers used) may not have been testedas safe excipients yet or they may be rather expensive. Furthermore,many of the systems may have a high cost of production because of thecombination of specially adapted machinery and expensive excipients theyrequire. Finally, many systems suffer from the fact that they are ratherfragile and their gastro-retentive performance may be seriouslycompromised in case of damage of the dosage form, e.g. a fissure orcrack in a coating layer, an edge broken from a tablet or inactivationof the effervescent system by moisture.

The above developments highlight the continuous need and industrialinterest for developing new gastric retention formulations that canreadily be developed, tested and manufactured. In view of this ongoingneed, the present inventors set out to provide an alternativegastro-retentive dosage form. They aimed in particular at thedevelopment of an economically attractive oral drug delivery systemallowing for the controlled and prolonged gastric residence of soliddrug dosage forms, which would readily be accepted by registrationauthorities and that was able to provide controlled release of thedrug(s) over periods between 1.5 and 24 hour after administration. Onefurther goal was to provide a floating system that is simple andrelatively cheap to manufacture. Yet a further goal was to provide asystem that is physically robust and/or does not loose itsgastro-retentive properties upon minor damage.

SUMMARY OF THE INVENTION

It was surprisingly found that at least some of these goals could be metby the provision of a floating drug delivery system (FDDS), comprising aparticle having a hollow, gas-filled core bordered by a wall of at leastone aqueous soluble, erodible, disintegrating or degradable material,typically a polymer, said wall being surrounded by a coating comprisingat least one active ingredient.

The present invention, in an aspect, provides a solution to theparticular problems encountered with many drugs that are absorbed(only/mainly) in the proximal site of small intestine. The formulationsfacilitate absorption of active ingredient into the systemic circulationfrom only a limited part of the (proximal) intestinal tract for anextended period of time after administration, by enhancing thegastro-rentention or gastric residence time of the delivery system,while continuously releasing active ingredient from the system.

Surprisingly, the present inventors established that, at least in somecases, the use of oral long acting formulations of the invention allowsfor effective and treatments, not only with fewer dosages per day, butalso with total daily dosages significantly below those suggested in theart.

In a particularly preferred embodiment of the invention, the floatingdrug delivery system (FDDS) comprises a coating containing a polymerthat swells upon contact with water. An FDDS according to thisembodiment has the advantage that it can maintain its buoyancy even when(severely) damaged. The vulnerability of floating drug delivery systemsis a generally recognized problem. Damaging of the drug delivery system,such as is often encountered during production, transportation and,especially, during ingestion (e.g. as a result of inadvertent chewingmotions by the subject taking the formulation), may easily make thegas-filled compartment accessible to water so as to impair its buoyancy,ultimately resulting in insufficient gastric residence time. A solutionto this problem is provided by the present invention, as will beillustrated in the appended examples.

The floating drug delivery systems of the invention, contrary to manyfloating dosage forms described in the art, allow for incorporation ofhigh loads of active ingredients, as will be apparent from the examples.

It has also been established that, in accordance with the invention,floating drug delivery systems can be developed wherein release ofactive ingredient from the system occurs entirely independent from thepH of the fluid surrounding the system.

Furthermore, in contrast to (multi)particulate floating dosage forms,the procedure of manufacturing the floating drug delivery system of theinvention is simple and straightforward, and therefore economicallyattractive, in particular when the particle is filled with air.

These and other aspects of the invention and its preferred embodimentswill be described in more detail and exemplified in the followingsections.

DETAILED DESCRIPTION OF THE INVENTION

A first aspect of the invention concerns a floating drug delivery system(FDDS), comprising a particle having a hollow, gas-filled core borderedby a wall of at least one aqueous soluble, erodible, disintegrating ordegradable material, said wall being surrounded by a coating comprisingat least one active ingredient.

A particularly preferred embodiment of the invention, a floating drugdelivery system (FDDS) is provided, comprising a particle having ahollow, gas-filled core bordered by a wall of at least one aqueoussoluble, erodible, disintegrating or degradable polymer, said wall beingsurrounded by a coating comprising at least one active ingredient.

In one embodiment, the invention provides a FDDS comprising a capsulehaving a hollow, gas-filled core bordered by a wall of at least oneaqueous soluble, erodible, disintegrating or degradable polymer, saidwall being surrounded by a coating comprising at least one activeingredient.

It will be understood that essentially any type of active ingredient canbe incorporated in the coating. The expression ‘active ingredient’refers to any compound having biological activity, or being capable ofbeing converted to such compound (e.g. a pro-drug). In embodiments ofthis inventions the term ‘active ingredient’ is synonymous for andinterchangeable with the terms ‘pharmacologically active ingredient’,‘pharmaceutically active ingredient’, ‘therapeutically acceptableingredient’, ‘drug’, etc. In embodiments of this invention, the term‘active ingredient’ also encompasses micronutrients, neutraceuticals,food supplements, probiotics, prebiotics, etc.

Examples of (pharmacologically/pharmaceutically) active ingredients thatcan benefit from using gastro-retentive drug delivery devices includedrugs acting locally in the stomach; drugs that are primarily absorbedin the stomach or, in particular, in the upper intestinal tract; drugsthat are poorly soluble at an alkaline pH; drugs with a narrow window ofabsorption; drugs absorbed rapidly from the GI tract; drugs that areabsorbed only or mainly in the proximal site of small intestine and/ordrugs that degrade in the lower intestinal tract or colon. It may be amaterial selected from the group consisting of AIDS adjunct agents,alcohol abuse preparations, Alzheimer's disease management agents,amyotrophic lateral sclerosis therapeutic agents, analgesics,anesthetics, antacids, antiarythmics, antibiotics, anticonvulsants,antidepressants, antidiabetic agents, antiemetics, antidotes,antifibrosis therapeutic agents, antifungals, antihistamines,antihypertensives, anti-infective agents, antimicrobials,antineoplastics, antipsychotics, antiparkinsonian agents, antirheumaticagents, appetite stimulants, appetite suppressants, biological responsemodifiers, biologicals, blood modifiers, bone metabolism regulators,cardioprotective agents, cardiovascular agents, central nervous systemstimulants, cholinesterase inhibitors, contraceptives, cystic fibrosismanagement agents, deodorants, diagnostics, dietary supplements,diuretics, dopamine receptor agonists, endometriosis management agents,enzymes, erectile dysfunction therapeutics, fatty acids,gastrointestinal agents, Gaucher's disease management agents, goutpreparations, homeopathic remedy, hormones, hypercalcemia managementagents, hypnotics, hypocalcemia management agents, immunomodulators,immunosuppressives, ion exchange resins, levocarnitine deficiencymanagement agents, mast cell stabilizers, migraine preparations, motionsickness products, multiple sclerosis management agents, musclerelaxants, narcotic detoxification agents, narcotics, nucleosideanalogs, non-steroidal anti-inflammatory drugs, obesity managementagents, osteoporosis preparations, oxytocins, parasympatholytics,parasympathomimetics, phosphate binders, porphyria agents,psychotherapeutic agents, radio-opaque agents, psychotropics, sclerosingagents, sedatives, sickle cell anemia management agents, smokingcessation aids, steroids, stimulants, sympatholytics, sympathomimetics,Tourette's syndrome agents, tremor preparations, urinary tract agents,vaginal preparations, vasodilators, vertigo agents, weight loss agents,Wilson's disease management agents, and mixtures thereof.

Examples of active ingredients that may be particularly suitable forincorporation in the FDDS of the invention include acetaminophen,acetylsalicylic acid, acyclovir, amoxycillin, ampicillin, aspirin,atenolol, baclofen, benserazide, bifosfonaten (alendronate), captopril,carbidopa, chlordiazepoxide, chlordiazepoxide, chlorpheniramine,cinnarizine, ciprofloxacin, cisapride, diazepam, diclofenac, diltiazem,florouracil, furosemide, gabapentin, ganciclovir, G-CSF, glipizide,griseofulvin, iboprufen, ijzer zouten, indomathacin, isosorbide,ketoprofen, levodopa, melatonin, metformine, minocyclin, misoprostol,nicardipine, nimodipine, p-aminobenzoic acid, pentoxyfillin, piretanide,p-nitroaniline, prednisolone, propranlol, quinidine gluconate,riboflavin, riboflavin-5′-Phosphate, sotalol, terfenadine, tetracycline,theophylline, tranilast, urodeoxycholic acid, ursodeoxycholic acid,verapamil and vitamin E

In an embodiment of the invention, the active ingredient is levodopa, ora salt ester, derivative, hydrate and/or solvate thereof. Levodopa isthe INN name for L-3,4-dihydrophenylalanine. In an embodiment of theinvention the active ingredient is a dopamine precursor or acatecholamine precursor. In an embodiment of the invention the activeingredient is a dopamine agonist. In an embodiment of the invention theactive ingredient is a combination of levodopa and carbidopa.

In an embodiment of the invention, the active ingredient isnicotinamide. Nicotinamide (IUPAC name pyridine-3-carboxamide), alsoknown as niacinamide and nicotinic acid amide, is the amide of nicotinicacid (vitamin B3/niacin). It will be understood by the skilled readerthat nicotinamide, as well as other compounds used in the presentinvention, may be capable of forming salts, complexes, hydrates andsolvates, and that the use of such forms in the defined treatments iscontemplated herein.

In a preferred embodiment, the active ingredient is not nicotinamide. Ina preferred embodiment the active ingredient is not nicotinamide or asalt, a complex, a hydrate or a solvate thereof. An embodiment of theinvention concerns a floating drug delivery system (FDDS), comprising aparticle, preferably a capsule, having a hollow, gas-filled corebordered by a wall of at least one aqueous soluble, erodible,disintegrating or degradable polymer, said wall being surrounded by acoating comprising at least one active ingredient, wherein said coatingcomprises a polymer that swells upon contact with water, with theexception of a floating drug delivery system (FDDS), comprising aparticle having a hollow, gas-filled core bordered by a wall of at leastone aqueous soluble, erodible, disintegrating or degradable polymer,said wall being surrounded by a coating comprising nicotinamide.

In a preferred embodiment a floating drug delivery system is providedthat, upon administration to a subject to be treated, is capable ofremaining in the stomach for a period extending over at least 2, atleast 3, at least 4, at least 5 or at least 6 hours, typically in thefasted state. In an embodiment the FDDS is capable of remaining in thestomach for a period extending over at least 12 or at least 24 hours,typically in the fasted state. Furthermore, in a preferred embodiment ofthe invention an FDDS is provided that, upon administration to a subjectto be treated, is capable of releasing active ingredient to the GIT(stomach and proximal small intestine) for a period extending over atleast 2, at least 3, at least 4, at least 5 or at least 6 hours,typically in the fasted state. In an embodiment the FDDS is capable ofreleasing active ingredient to the GIT for a period extending over atleast 12 or at least 24 hours, typically in the fasted state.Furthermore, in a preferred embodiment of the invention an FDDS isprovided that, in a standard in vitro test in a so called USPdissolution apparatus, is capable of releasing active ingredient fromthe delivery system in a so called slow release profile. Such a releaseprofile is preferably characterized by a release of less than 45% of thetotal active ingredient content after 1 hour and/or the release of morethan 30% and less than 75% after 3 hours and/or the release of less than80% after 6 hours. In an alternative embodiment the release profile ischaracterized by the release of less than 35% of the total activeingredient content after 1 hour and/or the release of more than 30% andless than 75% after 5 hours and/or the release of more than 80% of thetotal active ingredient content after 10 hours. In an alternativeembodiment the release profile is characterized by the release of lessthan 25% of the total active ingredient content after 1 hour and/or therelease of more than 30% and less than 75% after 12 hours and/or therelease of more than 80% of the total active ingredient content after 24hours.

Unless specified otherwise in this document, in vitro testing of theFDDS system is carried out in a so called USP dissolution apparatus II.With the dissolution medium (500 to 900 ml) at a temperature of 37° C.and a rotational speed of the paddle of 50 tot 75 RPM. For investigatingthe release profile or floating capacity of the gastro-retentivesystems, simulated gastric fluid of the following composition is used:sodium lauryl sulphate 2.5 g; sodium chloride 2.0 g; 0.01-0.05 Nhydrochloric acid in water 1000 ml. Active ingredient concentrations inthe dissolution medium can be determined by any suitable analyticalmethod, like ultraviolet absorption or HPLC analysis.

In a preferred embodiment of the invention an FDDS is provided, whichremains buoyant on the gastric fluid upon administration, typically toachieve the afore-defined goals. Usually the buoyancy is characterizedby the floating time (h) and/or buoyancy AUC (mg h). In a preferredembodiment of the invention a floating delivery system is providedhaving a floating time of at least 2, at least 3, at least 4, at least 5or at least 6 hours when tested in vitro in the USP dissolutionapparatus II. In an embodiment an FDDS is provided having a floatingtime of at least 12 or at least 24 hours when tested in vitro in the USPdissolution apparatus II.

Preferably, in the FDDS of the invention, active ingredient is presentin a coating that encompasses or surrounds a solid particle made of atleast one aqueous soluble, erodible, disintegrating or degradablepolymer (e.g. by coating onto the surface of the particle), saidparticle having a hollow, gas-filled core bordered by a wall of at leastone degradable polymer. As will be understood, the gas is a non-toxicgas. Air is the preferred gas. Because of the gas-filled compartment,lacking any particulate matter or matrix components, an FDDS providedherein having unique floating capacity and therefore very good gastricretention properties. Using an established in vitro gastric fluidsimulation system, a floating time of at least up to 24 hours wasobserved. Thus, provided herein is gastric retention device capable ofremaining in the stomach for at least 6, preferably at least 9, morepreferably at least 12 hours. Also provided is the use of an air-filledcapsule, generally lacking any therapeutically active ingredient, as afloating carrier for a drug in a gastro-retentive drug formulation.

According to the invention, the active ingredient is present in an outerlayer or coating that controls not only the penetration of liquid (e.g.gastric fluid) into the particle, but also the release of activeingredient from the particle. Thus, in contrast to floating systemsknown in the art comprising (sub)compartments or chambers filled withair, such as floating microspheres, the present invention isconceptually different in that the active ingredient is present on theexterior of the gas filled compartment, and essentially absent (at leastupon manufacture) from the inner core of a particle.

As will be explained below, the particle may be a conventional gelatinor HPMC capsule known in the art, which is easily provided with acoating comprising active ingredient. The system can be produced usingonly excipients that are known to be safe for human or animal use andthat are accepted by regulatory authorities.

Typically, the particle in the FDDS of the invention itself will lackany therapeutically active ingredient and only contains activeingredient in the external coating layer. However, it is alsoencompassed that a small (e.g. up to about 50%, preferably up to 35% or30%, more preferably up to 20%, like 5, 10, 12, 15 or 17%) volume of thecapsule or other type of hollow particle is filled with activeingredient, or another active ingredient, as long as the overall densityof the capsule remains sufficiently low to allow for floating.Therefore, also provided is the use of a capsule of which only 50% orless, preferred is 35% or less even more preferred 20% or less, of thevolume is filled with active ingredient or another active ingredient andthe remaining volume is gas-filled as floating carrier for a drug in agastro-retentive drug formulation. Only when the capsule erodes ordisintegrates, its content is released. This may for instance beadvantageous for applications wherein it is desirable to provide a final“burst” dose of the drug at the end of the release period. For example,a FDDS comprising the majority of active ingredient in the particlecoating and a minor fraction within the coated particle allows achievinglow yet sustained blood drug levels during the night, followed by anincreased drug level in the morning. This is especially advantageous forthe treatment of diseases wherein symptoms are worse in the morning,such as rheumatoid arthritis (RA) or asthma.

To protect the stomach lining to continued exposure of certain activeingredients, an embodiment is envisaged wherein the FDDS contains theactive ingredient in microencapsulate form, which microencapsulates aredispersed within the external coating layer of the FDDS. Themicroencapsulate typically contains a core comprising or consisting ofactive ingredient covered by a layer of enteric polymer, designed todissolve upon entry of the released microcapsules from the stomach intothe small intestine. Alternatively the microencapsulate may simplycomprise particles containing active ingredient dispersed within anenteric polymer matrix, designed to dissolve upon entry of the releasedmicroencapsulate from the stomach into the small intestine.

The skilled person will be able to select the appropriate materials toobtain a coating, and optionally a micorencapsulate for incorporation insaid coating, yielding the desired characteristics with respect toliquid penetration and the release of the active ingredient inaccordance with the afore described embodiments.

In a preferred embodiment of the invention, an FDDS as defined herein isprovided, comprising a coating layer containing active ingredient in anamount of at least 40 wt. %, at least 50 wt. %, at least 60 wt. %, atleast 70 wt. %, at least 75 wt. %, or at least 80 wt. %, based on thetotal weight of said coating layer, of active ingredient.

The active ingredient may be present in two or more layers of thecoating, each layer having a distinct composition. It is also possibleto provide the particle with a “subcoating” and/or “topcoating” toachieve a desired GRT and/or release profile. A single coating layercomprising active ingredient may be preferable in some embodiments forreasons of simplicity. However, in other preferred embodiments severallayers of coatings may be applied, typically having distinctcompositions and active ingredient amounts. As will be shown in theexamples, the use of two or three coating layers having distinct releaseprofiles allows for the design of formulations capable of near constantactive ingredient release over periods of up to 12 hours. In one suchembodiment an FDDS is provided comprising three coating layers, whereinthe inner layer comprises 50-90 wt %, 60-87 wt % or 70-85 wt % of activeingredient, based on the total weight of the inner coating layer; themiddle layer comprises 30-70 wt %, 40-60 wt % or 45-55 wt % of activeingredient, based on the total weight of the middle coating layer; andthe outer layer comprises less than 10 wt %, less than 5 wt % or lessthan 1 wt % of active ingredient based on the total weight of the outercoating. In another embodiment an FDDS is provided comprising twocoating layers, wherein the inner layer comprises 50-90 wt %, 60-87 wt %or 70-85 wt % of active ingredient, based on the total weight of theinner coating layer; and the outer layer comprises less than 10 wt %,less than 5 wt % or less than 1 wt % of active ingredient based on thetotal weight of the outer coating layer.

The coating materials of the one or more coating layers may be selectedfrom the group consisting of coating materials resistant to gastricjuice, release-controlling polymers, and mixtures thereof.Release-controlling polymers are well known in the art of drugformulations for controlled (e.g. sustained) release, and includeswellable polymers, or polymers that are poorly water-soluble orwater-insoluble. Exemplary release controlling polymers are hydrophiliccellulose derivatives (such as HPMC, HPC, MC, HEC, CMC, sodium-CMC),PVP, PVA, Carboxyvinyl polymer (Carbomer), Poly(ethyleneoxide) (PolyoxWSR), alginates, pectins, guar gum, vinylpyrrolidone-vinyl acetatecopolymer, dextrans, carrageenan, gellan, hyaluronic acid, pullulan,scleroglucan, xanthan, xyloglucan, chitosan, poly(hydroxyethylmethacrylate), ammoniomethacrylate copolymers (such as Eudragit RL orEudragit RS), Poly(ethylacrylate-methylmethacrylate) (Eudragit NE), andEthylcellulose. The coating may comprise a mixture of at least tworelease controlling polymers. For instance, a combination of HPMC andEudragit RL was found to be very useful. Eudragit RL PO is a polymer forcontrolled release drug formulation. Due to the insolubility in the acidfluids of the stomach it is able to give a release of active ingredientsover the desired period of time.

In another preferred embodiment, the invention provides a floating drugdelivery system comprising a particle having a hollow, gas-filled corebordered by a wall, as defined herein, and comprising one or morecoating layers comprising a combination of HPMC and starch as coatingmaterial, typically in a ratio within the range of 8:1-1:1, preferably6:1-2:1, more preferably 5:1-3:1, most preferably about 4:1. The use ofhypromellose was found to favourably delay active ingredient release.

In a particularly preferred embodiment of the present invention, saidstarch is pregelatinized starch.

In another preferred embodiment, the invention provides a floating drugdelivery system comprising a particle having a hollow, gas-filled corebordered by a wall comprising one or more coating layers comprising acombination of HPMC and pregelatinized starch as coating material,typically in a ratio within the range of 1:1-1:8, preferably 1:1-1:6,more preferably 1:1-1:5, most preferably 1:1-1:4. As will be evidentfrom the appending examples, the combination of hypromellose andpregelatinized starch is very advantageous in that it allows foraccurate programming of active ingredient release, depending on thechoice and nature of the active ingredient.

In preferred embodiments of the invention, an FDDS is providedcomprising at least two active ingredient containing coating layers,e.g. as described here above, having distinct ratios of hypromellose andstarch, the outer layer typically comprising a larger amount ofhypromellose, relative to starch, than the inner layer.

In a particularly preferred embodiment of the present invention, saidstarch is pregelatinized starch.

In another preferred embodiments of the invention, an FDDS is providedcomprising an active ingredient containing inner coating layer, e.g. asdescribed here above, as well as an outer coating layer that does notcontain active ingredient. The use of an outer coating layer allows foraccurate programming of active ingredient release, as will beillustrated in the appended examples. In an embodiment, the inner andouter coating layers comprise hypromellose and pregelatinized starch.The inner and outer layer may comprise hypromellose and pregelatinizedstarch in the same (relative) amounts. In an embodiment the outer layertypically comprises a larger amount of hypromellose, relative topregelatinized starch, than the inner layer.

Furthermore, it has been established that coating layers comprisinghypromellose or other water-swellable polymers maintained theirfavourable release profile and floating properties when mechanicallydamaged or even ruptured, as will be illustrated in the examples herebelow.

Finally, it was established that the FDDS produced with thesecompositions was physically strong and robust, with crushing strengthsfar over 100 N. Hence, in an embodiment of the invention, an FDDS asdefined herein is provided having a crushing-strength of at least 100 N,more preferably of at least 150 N.

Hence, a preferred embodiment of the invention concerns the FDDS asdefined herein, and its use, wherein a polymer is used that swells uponcontact with water, so as to render the FDDS ‘self-repairing’. Mostpreferably said water-swellable polymer is hypromellose. In anembodiment of the invention, said water-swellable polymer is nothypromellose.

A particularly preferred embodiment of the invention concerns a floatingdrug delivery system (FDDS), comprising a particle, preferably acapsule, having a hollow, gas-filled core bordered by a wall of at leastone aqueous soluble, erodible, disintegrating or degradable polymer,said wall being surrounded by a coating comprising at least one activeingredient, wherein said coating comprises a polymer that swells uponcontact with water.

Another preferred embodiment of the invention concerns a floating drugdelivery system (FDDS), comprising a particle, preferably a capsule,having a hollow, gas-filled core bordered by a wall of at least oneaqueous soluble, erodible, disintegrating or degradable polymer, saidwall being surrounded by a coating comprising at least one activeingredient, wherein said coating comprises hypromellose or anotherwater-swellable polymer.

Another preferred embodiment of the invention concerns a floating drugdelivery system (FDDS), comprising a particle, preferably a capsule,having a hollow, gas-filled core bordered by a wall of at least oneaqueous soluble, erodible, disintegrating or degradable polymer, saidwall being surrounded by a coating comprising at least one activeingredient, wherein said floating drug delivery system maintains itsrelease profile and floating properties when mechanically damaged orruptured

Another preferred embodiment of the invention concerns a floating drugdelivery system (FDDS), comprising a particle, preferably a capsule,having a hollow, gas-filled core bordered by a wall of at least oneaqueous soluble, erodible, disintegrating or degradable polymer, saidwall being surrounded by a coating comprising at least one activeingredient, wherein a polymer is used that swells upon contact withwater, so as to render the FDDS self-repairing.

Another preferred embodiment of the invention concerns a floating drugdelivery system (FDDS), comprising a particle, preferably a capsule,having a hollow, gas-filled core bordered by a wall of at least oneaqueous soluble, erodible, disintegrating or degradable polymer, saidwall being surrounded by a coating comprising at least one activeingredient, wherein said coating comprises a water-swellable polymerother than hypromellose.

Another preferred embodiment of the invention concerns a floating drugdelivery system (FDDS), comprising a particle, preferably a capsule,having a hollow, gas-filled core bordered by a wall of at least oneaqueous soluble, erodible, disintegrating or degradable polymer, saidwall being surrounded by a coating comprising at least one activeingredient, wherein said coating comprises a water-swellable polymer isnot hypromellose.

Typically, by “water swellable polymer” is meant a polymer that does notreadily dissolve in water (or does not dissolve in water at all) butinteracts with water to cause the polymer to increase in volume. Waterswellable polymers useful in the preparation of the FDDS of thisinvention include polymers that are non-toxic and that swell in adimensionally unrestricted manner upon imbibition of water and hence ofgastric fluid. Examples of polymers meeting this description are:cellulose polymers and their derivatives including, but not limited to,hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropylcellulose, hydroxypropylmethyl cellulose, and carboxymethylcellulose;polysaccharides and their derivatives; polyalkylene oxides; polyethyleneglycols; chitosan; poly(vinyl alcohol); xanthan gum; maleic anhydridecopolymers; poly(vinyl pyrrolidone); starch, in particularpregelatinized starch, and starch-based polymers; carbomer;maltodextrins; amylomaltodextrins, dextrans, poly (2-ethyl-2-oxazoline);poly(ethyleneimine); polyurethane hydrogels; and crosslinked polyacrylicacids and their derivatives. Further examples are copolymers of thepolymers listed above, including block copolymers and graft polymers.Specific examples of copolymers are PLURONIC® and TECTONICS®, which arepolyethylene oxide-polypropylene oxide block copolymers availablecommercially. Further examples are hydrolyzed starch polyacrylonitrilegraft copolymers.

In a particularly preferred embodiment of the invention concerns afloating drug delivery system (FDDS), comprising a particle, preferablya capsule, having a hollow, gas-filled core bordered by a wall of atleast one aqueous soluble, erodible, disintegrating or degradablepolymer, said wall being surrounded by a coating comprising at least oneactive ingredient, wherein said coating comprises a polymer selectedfrom the group consisting of hydrophilic cellulose derivatives, such asHPMC, HPC, MC, HEC, CMC, sodium-CMC); PVP; PVA; carboxyvinyl polymer(carbomer); poly(ethyleneoxide) (polyox WSR), alginates, pectins, guargum, vinylpyrrolidone-vinyl acetate copolymer; dextrans; carrageenan;gellan; hyaluronic acid; pullulan; scleroglucan; xanthan; xyloglucan.

In a preferred embodiment of the invention, an FDDS as defined herein isprovided, wherein at least 50 wt. %, at least 60 wt. %, at least 70 wt.%, at least 75 wt. %, at least 80 wt. %, at least 85 wt. %, at least 90wt. % or at least 95 wt. % of the coating excipients, i.e. of thematerials contained in the coating other than the active ingredient(s),is a water-swellable polymer as defined in the foregoing.

The FDDS coating may also comprise one or more enteric polymer coatingmaterials. The term “enteric polymer” is a term of the art referring toa polymer which is preferentially soluble in the less acid environmentof the intestine relative to the more acid environment of the stomach.Useful enteric polymers for practising the present invention includecellulose acetate phthalate, cellulose acetate succinate,methylcellulose phthalate, ethylhydroxycellulose phthalate,polyvinylacetatephthalate, polyvinylbutyrate acetate, vinylacetate-maleic anhydride copolymer, styrene-maleic mono-ester copolymer,methacrylic acid methylmethacrylate copolymer, methylacrylate-methacrylic acid copolymer, methacrylate-methacrylic acid-octylacrylate copolymer, and combinations thereof.

In a specific aspect, the invention provides a delivery systemcomprising a particle having a hollow, gas-filled core bordered by awall of at least one aqueous soluble, erodible, disintegrating ordegradable material, typically a polymer, said wall being surrounded bya coating comprising at least one enteric polymer and active ingredient,preferably wherein the enteric polymer is a pharmaceutically acceptablemethacrylic acid methylmethacrylate copolymer, such as a polymer soldunder the trade name Eudragit™, including polymers from the Eudragit RLor Eudragit RS series. Again, mixtures of different types of coatingpolymers may be used. In one embodiment, the coating comprises a mixtureof an enteric polymer, such as Eudragit RL, and a release controllingpolymer, preferably a water-swellable release controlling polymer. As isexemplified below, a combination of HPMC and Eudragit RL, for instancein relative weight ratio's of between 1:2 and 2:1, give very goodresults.

In addition to the coating polymer(s), a coating may comprise one ormore additives having a beneficial or otherwise desired effect on aproperty of the coating. Useful additives include a plasticizer, astabiliser, a pH adjuster, a GI motility adjuster, a viscosity adjuster,a diagnostic agent, an imaging agent, an expansion agent, a surfactant,and mixtures thereof.

In one embodiment, the coating comprises a plasticizer. The group ofplasticizers contains, but is not limited to, materials such as PEG6000(also known as Macrogol 6000), triethyl citrate, diethyl citrate,diethyl phthalate, dibutyl phthalate, tributyl citrate, and triacetin.The quantity of plasticiser included will be apparent to those skilledin the art. Typically the coating may include around 2-15 wt. %plasticiser based on the total dry weight of the coating. The entericcoating may also include an anti-tack agent such as talc, silica orglyceryl monostearate.

As will be understood, floating dosage forms rely on their ability tofloat on gastric fluid. Gastric fluid has a density close to that ofwater, which is 1.004 g/ml. Therefore, for the system to remain afloat,the overall density of the system must be less than 1 g/ml. In oneembodiment, a drug delivery system according to the invention has adensity of less than 0.95 g/cm³. Lower densities, such as less than 0.9g/cm³, more preferably less than 0.8 g/cm³ are of course preferred. In aspecific aspect, the density is less than 0.7 g/cm³.

Of particular interest is the inclusion in the coating comprising activeingredient of an effervescent (gas forming) compound, i.e. an agentcapable of generating CO₂ in situ upon contact with acid such as gastricfluid. This will provide the FDSS of the invention with additionalbuoyancy. Effervescent compounds are used already in the art of floatingdosage forms and include sodium bicarbonate, sodium carbonate, or sodiumglycine carbonate. However, the use of effervescent compounds has beenlimited primarily to either (a) single layer systems wherein gas formingmaterial is mixed with the drug or (b) multiparticulate unit systemscomprising a conventional sustained release pill, coated with a bilayersystem consisting of an inner effervescent layer and an outer layer ofswellable membrane (see Bardonnet et al. J Control Release 2006;111(1-2)1-18).

The wall of the gas-filled particle is made of an aqueous soluble,erodible, disintegrating and/or biodegradable material, typically apolymer, such that the floating drug delivery system leaves no tracebehind in the body. Suitable polymers that are aqueous soluble,erodible, disintegrating and/or biodegradable are well known in the art,and include gelatine and hydroxypropyl methylcellulose (HPMC).

The shape and size of the particle can vary. Of course, for oraladministration purposes it is preferred that the particle can beswallowed. A preferred particle is a conventional gastricerodible/soluble capsule, such as a gelatine capsule or a HPMC capsule.Soft shells are also encompassed. The particle can be a single or amultiparticulate capsule. In one embodiment, the invention provides aFDDS comprising a capsule having a hollow, gas-filled core bordered by awall of at least one aqueous soluble, erodible, disintegrating ordegradable material, typically a polymer, said wall being surrounded bya coating comprising at least one active ingredient. In view of gastricretention time, it is preferred that an oral gastro-retentive dosageform is as large as possible (to minimize passage through the pylorus)yet sufficiently small to be swallowed. Preferably, a FDDS providedherein comprises an oblong shaped capsule having a length of at least 10mm, preferably at least 14 mm, more preferably at least 16 mm, mostpreferably at least 19 mm, and/or a diameter of at least 5 mm preferablyat least 6 mm, more preferred at least 7, most preferred at least 8 mm.Suitable capsules include those referred to in the art as Type 5, 4, 3,2, 2e1, 1, 1e1, 0, 0e1, 00, 00e1 or 000 capsules. Alternatively, widebody capsules (BDCaps®) may be used. These capsules are referred to inthe art as E, D, C, B, A, AA, AAel or AAA.

The FDDS as described herein provides an alternative gastro-retentivedosage form that is simple and relatively cheap to manufacture. Afloating drug delivery system (FDDS) comprising active ingredient can beprepared using a method comprising the steps of (a) providing agas-filled particle made of at least one aqueous soluble, erodible,disintegrating or degradable polymer and (b) providing a coatingsolution or a coating dispersion comprising active ingredient, a coatingpolymer, optionally additives, in a volatile solvent. Then, at least onelayer of coating dispersion is applied onto the surface of particle,typically by spraying or dip coating. Application may be direct onto theaqueous soluble, erodible, disintegrating or degradable material,typically a polymer, making up the wall of the particle. Alternatively,the wall may first be provided with a sub-coating, on which the coatingcomprising active ingredient is applied. Upon the evaporation of thevolatile solvent, a solid coating serving as “drug release layer” isobtained. Furthermore the active ingredient-containing layer may becovered by a top-coating that improve the appearance of the capsule(e.g. giving it a colour) or contain taste-masking components. Step (a)preferably entails the manufacture of a conventional air-filled capsuleaccording to well-established methods. The capsule can be a two-partconventional capsule as well as a single unit air filled capsule. Step(b) in itself is also standard practice in the art of controlled releasedosage forms. The skilled person will be able to choose the type(s) andrelative amount(s) of the components to obtain a coating solution or acoating dispersion that provides the particle with a drug coating havingthe desired release properties. A suitable volatile solvent is analcohol, such as ethanol or isopropanol. Alternatively aqueous solutionsor suspensions could be used. The solution or dispersion may containbetween about 10 and 600 gram of dry matter per liter solvent, such asbetween 50 and 150 gram per liter. The concentrations and relativeamount of active ingredient in the coating dispersion may depend on thedosage amount to be achieved. In general, the coating dispersion willcontain between about 1 and 50 wt % of active ingredient based on thetotal dry weight of the dispersion. It is important that the coatingdispersion is sufficiently homogeneous to obtain a good coatinguniformity. This can be achieved by thorough mixing. When dip coating isapplied even higher amounts of dry matter could be added to the volatilesolvent. An aspect of the invention relates to the above-describedmethods for providing a floating drug delivery system (FDDS).

As will be illustrated in the examples here below, the FDDS of thepresent invention can be loaded with relatively high amounts of activeingredient, i.e. as compared to other types of floating drug deliverysystems. Depending on the target subject and/or dosage regimen, suitabledosage forms of the FDDS can be developed. In one embodiment, the FDDScomprises a particle (capsule) having a hollow, gas-filled core borderedby a wall of at least one aqueous soluble, erodible, disintegrating ordegradable polymer, said wall being surrounded by a coating comprising10 mg to 10 gram of active ingredient. Preferably, the coating comprises20 to 8000 mg of active ingredient, more preferably 25 to 5000, such as20-1000, 50-500 or 1000-2500. Preferred examples of the FDDS of theinvention contain active ingredient in a total amount of 100, 150 mg,200 mg, 250 mg, 300 mg, 400 mg, 500 mg or 600 mg.

A floating drug delivery system as provided herein is advantageouslyused for the treatment or prophylaxis of a disease, for example in amethod comprising administering to a patient in need thereof acomposition comprising a floating drug delivery system (FDDS) accordingto the invention, wherein the at least one active ingredient is capableof treating or preventing the disease. The FDDS is preferably formulatedfor oral administration. In one embodiment, a method of the inventioncomprises administering to a patient in need of such treatment orprophylaxis a composition comprising an oral floating drug deliverysystem (FDDS), the system comprising a controlled release coatingcomprising at least one active ingredient against the disease coatedonto the surface of a solid particle, said particle having a hollow,gas-filled core bordered by a wall of at least one aqueous soluble,erodible, disintegrating or degradable material, typically a polymer. Itwill be understood that an FDDS of the invention, as with other floatingsystems, works optimal if the stomach of the subject receiving the FDDSis at least partially filled with gastric fluid. Therefore, it ispreferred that the subject is a non-fasted subject. In case the subjectis a fasted subjects, the method comprises administering to the subjectan oral floating drug delivery system (FDDS) together with a sufficientamount of fluid, e.g. an amount of water of at least 100 ml, preferablyat least 200 ml.

In one aspect, the invention provides a method for treating orpreventing a disease which is located in the stomach or upper intestinaltract, comprising administering to a patient in need thereof acomposition comprising a floating drug delivery system (FDDS) accordingto the invention, and wherein the active ingredient is useful in thelocal treatment of the disease. In another aspect, the inventionprovides a method for treating or preventing a disease, comprising oralsystemic drug administration, and wherein the active ingredient isabsorbed into the systemic circulation from only a limited part of theintestinal tract.

A FDDS of the invention is particularly useful for delivering atherapeutic agent to the stomach or upper intestinal tract of a patientand/or for enhancing the gastric retention of an agent in the stomach ofa patient, the method comprising oral administration to the patient of acomposition comprising a floating drug delivery system (FDDS), wherein acoating comprising the therapeutic agent is coated onto the surface of asolid particle, preferably a capsule, said particle having a hollow,gas-filled core bordered by a wall of at least one aqueous soluble,erodible, disintegrating or degradable material, typically a polymer.

Also encompassed is a method of enhancing the gastrointestinalabsorption of a drug which is absorbed into the systemic circulationover only a limited part of the small intestine of a patient, the methodcomprising oral administration to the patient of the drug beingincorporated in a FDSS as provided herein.

As will be understood by those skilled in the art, the principalfeatures of this invention can be employed in the various aspects andembodiments without departing from the scope of the invention. More, inparticular, it is contemplated that any feature discussed in thisspecification can be implemented with respect to any of the methods,compositions and uses of the invention, and vice versa.

Furthermore, for a proper understanding of this invention and itsvarious embodiments it should be understood that in this document andthe appending claims, the verb “to comprise” is used in its non-limitingsense to mean that items following the word are included, but items notspecifically mentioned are not excluded. In addition, reference to anelement by the indefinite article “a” or “an” does not exclude thepossibility that more than one of the element is present, unless thecontext clearly requires that there be one and only one of the elements.The indefinite article “a” or “an” thus usually means “at least one”.

The following examples describe various new and useful embodiments ofthe present invention. It will be understood that particular embodimentsdescribed herein are shown by way of illustration and not as limitationsof the invention. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, numerousequivalents to the specific procedures described herein. Suchequivalents are considered to be within the scope of this invention andare covered by the claims.

Example 1

A typical example of a gastro-retentive system can be obtained bycoating of an empty gelatine capsule with coating comprising at leastone pharmacologically active ingredient.

In a specific embodiment the gelatine capsule is coated with asuspension containing:

-   -   drug (e.g. nicotinamide): 1 to 95% of the solids in the        suspension;    -   polymers and release controlling agents: 5 to 99% of the solids        in the suspension.

The amount of drug that will be sprayed onto the capsule is determinedby the desired dose of the drug and the concentration of the drug in thecoating. The composition of the drug containing coating layer isdetermined by the desired release profile. Typical polymers likeHypromellosum 4000 mPa·s., viscosity 2% m/V or Eudragit RL PO can beused whereas plasticizers such as Polyethylenglycolum 6000 or dibutylphthalate can be used. Other excipients that can be used in the coatingsuspension are magnesium stearate, talc or mannitol. The coatingsuspension is applied on the gelatine capsules in equipment such asfluidized beds or perforated pan-coaters.

A second example of a gastro-retentive system can be obtained by theincorporation of gas-forming materials in a tablet that contains ahydrophilic gel forming polymer.

In a specific embodiment such a tablet would contain:

-   -   drug 0.5 to 90%;    -   HPMC 4000 10 to 80%;    -   sodium carbonate 5 to 20%;    -   Sodium stearyl fumarate 0.5 to 5%.

Furthermore excipients such as fillers, binders, glidants, lubricantsand others known in the art of tablet formulation can be added to theformulation. The tablets can be made according to well known tabletproduction technologies such as direct compaction, dry granulation orwet granulation techniques. Tablet compaction can be performed usingtablet machines widely known in the pharmaceutical industry.

Example 2: Dissolution of Nicotinamide from FDDS Materials

HPMC (Hypromellosum 4000 mPa·s., viscosity 2% m/V) was obtained fromBufa BV, Uitgeest, The Netherlands. Macrogol 6000 (Polyethylenglycolum6000) was obtained from Fagron, The Netherlands. Eudragit RL PO (PharmaPolymere, Röhm GmbH) was obtained from Chemische Fabric, Kirschenallee,Darmstadt, Germany. Nicotinamide Ph.Eur.quality was used.

Methods

A number of different coating dispersions (also referred herein as“suspensions”) were prepared (see Table 1). The required amount of HPMCwas weighted to a beaker and then mixed with Ethanol (100 ml).Subsequently, the nicotinamide was added in the amounts indicated below.In parallel, in another beaker Macrogol 6000 was prepared by melting ata temperature not higher than 80° C., after melting, ethanol (50 ml) wasadded and subsequently the required amount of Eudragit RL PO was added.The cooled solution was mixed with the contents of the first beaker toprovide a coating dispersion.

TABLE 1 composition of the different coating suspensions. IngredientCoating 1 Coating 2 Coating 3 HPMC 4.0 g 4.0 g 5.0 g Eudragit RL PO 3.5g 3.5 g 3.5 g Macrogol 6000 1.0 g 1.0 g 1.0 g nicotinamide 5.0 1.0 5.0ethanol 150 ml 150 ml 150 ml

Hard gelatine capsules (No. 3) were coated with the different coatingdispersions using an appropriate spray nozzle according to standardprocedures. Briefly, the coating dispersion was sprayed onto the surfaceof the capsules rotating in a small container under a heated air streamuntil the required amount of drug-polymer mixture as determined byweight analysis was sprayed on the capsules.

Dissolution test were performed in a beaker with 500 ml of 0.1 M HCl atpH=1.03-1.09 at a temperature of 34-38° C. while stirring at 150 rpmusing a magnetic stirrer.

Samples (2.5 ml) were taken every 30 minutes up to 7 hours with asyringe. The samples were analysed at 280 nm for the content of activeingredients using a spectrophotometer.

Results

Four capsules were coated with coating dispersion 1, and two of themwere subjected to the dissolution test in a beaker with 500 ml of 0.1NHCl. After six hours, more than 95% of active substance was released,showing that drug release was complete after 6 hours. The capsule wasstill floating on the 0.1N HCl after 24 hours.

Coating dispersion 2 was used to coat four capsules, and two of themwere subjected to the dissolution test. After six hours, more than 90%of active substance was released. The capsule was still floating on the0.1N HCl after 24 hours.

Coating dispersion 3 was used to coat another four capsules and two ofthem were subjected to the dissolution test. After six hours, less than50% of active substance was released. The higher quantity of HPMC incoating 3 leads to a slower release of active substance. Moreover therelease was incomplete. This shows that, by varying the polymer contentof the coating composition, the rate of drug release from the floatingparticle can be altered. The capsule was still floating on the 0.1N HClafter 24 hours.

Example 3: Development of a 300 mg and a 600 mg Nicotinamide GradientFDDS Background

The concept of an FDDS comprising several layers of distinct compositionand distinct amounts of nicotinamide was tested. Also the concept of anFDDs comprising an outer coating layer comprising no nicotinamide wastested.

The aim of the experiment was to optimize the formulation, especially toprevent an initial release burst and to prolong the period of constantnicotinamide release, preferably over the entire residence time of theFDDS in the stomach. This involved testing of formulations containingouter coatings containing a high percentage of hypromellose and outercoatings containing no nicotinamide as well as formulations containingan inner layer with a high percentage of starch.

Materials & Methods

Nicotinamide was purchased from Sigma-Aldrich, hypromellose 400 mPa·sfrom Bufa, Starch 1500 from Colorcon and magnesium stearate fromGenfarma by. In all experiments demineralized water was used. Therelease profiles were determined in 0.01N HCl. For the preparation ofcoating suspensions acetone was used.

Hypromellose is a swelling agent that is used to delay the release ofnicotinamide. The hydrophilic drug is released via diffusion. Starch andmagnesium stearate show a faster release of nicotinamide. This influenceof the various excipients has been investigated

To prepare the floating delivery system, a suspension containing theexcipients and the drug were sprayed on empty hollow capsules. This wasdone using a spray-coat system. The different substances are dissolvedin water and acetone. The suspension should be slightly viscous toprevent sedimentation and blockage in the system. The ratio of acetoneand distilled water depends on the amount of hypromellose. At a lowconcentration of hypromellose relatively more water is used so that thesuspension has the desired viscosity. The substances are first suspendedand/or dissolved in acetone prior to adding water. This preventsformation of lumps in the slurry. The suspension is sprayed through anozzle (1 mm) together with air, so that small droplets are introducedinto the spraying sphere. The spraying sphere is heated from the outsideso that the acetone evaporates quickly and the substances are coated onthe capsules. Capsule sizes 3, 4 and 5 (Spruyt Hillen) were used invarious experiments. It was decided that capsule size 4 was used whichwere ‘locked’ by pressing the halfs together so as to somewhat reducethe size.

The coatings consisted of different formulations with differentconcentrations of nicotinamide, hypromellose, magnesium stearate andstarch, as will be described here below.

The produced capsules were tested for their floating behaviour andrelease profile in a dissolution bath (Prolabo) filled with 1 liter0.01N HCl, 37±1° C., at 50 rpm. The 0.01N HCl was prepared by degassing6 liter of demineralized water and adding 8 ml 25% HCl. The releaseprofiled were determined for at least 12 hours by UV absorbancemeasurements at 280 nm (cuvet 1 cm) (Ultrospec III, Pharmacia LKB). Thefloating behaviour was followed by visual inspection. All experimentswere performed in 2-, 3- or 5-fold.

The final formulation for a 300 mg gradient FDDS comprises 3 layers. Thefirst layer surrounding the capsule has a concentration of 80%nicotinamide (200 mg active). The second layer 50% (100 mg active), andthe third layer 0% (90 mg coating material). The composition is shown inTable 2.

TABLE 2 composition of 300 mg nicotinamide FDDS. Component 80% 50% 0%Nicotinamide 79% 49% — Hypromellose 16% 40% 78% Starch 1500  4% 10% 20%Magnesium stearate  1%  1%  2% Amount of active 200 mg 100 mg —

The final formulation for the 600 mg gradient FDDS comprises 2 layers.The inner layer consists of 80% nicotinamide. The layer comprises 750 mgof the coating material. Around it is a 0% coating of 150 mg. A SEMimage was made of a cross-section of the FDDS in which both layers couldclearly be distinguished. The composition of this FDDS is shown in Table3.

TABLE 3 composition of 600 mg nictoinamide FDDS. Component 80% 0%Nicotinamide 79% — Hypromellose 16% 78% Starch 1500  4% 20% Magnesiumstearate  1%  2% Amount of active 600 mg —

RESULTS

FIGS. 1 and 2 show the release profiles of the 300 mg FDDS and 600 mgFDDS respectively. A satisfactory release rate is accomplished nearlyover the entire 12 hour period. The results show that the releaseprofiles of the 300 en 600 mg FDDS's are comparable.

The floating behaviour of both the FDDS's was also tested in milk,simulating an environment containing substantial amounts of fat. TheFDDS's staid afloat for more than 12 hours.

Discussion/Conclusion

The 300 and 600 mg nicotinamide gradient FDDS's are capable of stayingafloat for at least 12 hours and of releasing nicotinamide at asubstantially constant rate for almost the entire 12 hour period.

To achieve this near constant release the FDDS's were designed tocomprise different layers of coating. For example, the 300 mg FDDScontained an inner layer with 200 mg nicotinamide (80% based on thetotal weight of the layer), a middle layer with 100 mg nicotinamide (50%based on the total weight of the layer) and an outer layer that did notcontain nicotinamide. The 600 mg FDDS contained an inner layer with 600mg nicotinamide (80% based on the total weight of the layer) and anouter layer that did not contain nicotinamide.

The use of distinct layers allowed for the regulation of the overallrelease profile, to achieve near constant release rates of periods of upto 12 hours.

Example 4: Effects of Rupture of FDDS on Floating Capability and ReleaseProfile Background

The present inventors decided to also investigate the effects ofmechanical damage to the FDDS. It was envisaged that damaging of theformulation could easily arise when treating young children as theymight, for instance, ‘accidentally’ chew or crush the FDDS beforeswallowing. The floating behaviour and release profiles of rupturedcapsules were therefore tested and compared to the floating behaviourand release profiles of intact FDDS's.

Materials & Methods

The FDDS's used for this experiment were of the multi-layer gradienttype. They were prepared and tested using the protocols described inexample 3. The composition is shown in table 4.

TABLE 4 composition of FDDS for rupturing experiment 80% 50% 0%Hypromellose 16% 19% 78% Starch 1500  4% 10% 20% Magnesium stearate  1% 1%  2% Nicotinamide 79% 50% — Each FDDS contained 45 mg 0% coating.

The FDDS's proved to be strong and difficult to damage. The FDDS's wereplaced in a bench vice that was tightened until the wall of the FDDSbegan to rupture. The crushing strength was over 200 N for all products.

The floating behaviour as well as the release profile was determined ofboth the damaged and undamaged the FDDS's.

Results

All FDDS's, ruptured and undamaged, staid afloat in the testing liquid.After 18 hours remains were still afloat in the dissolution beakers.

The release profiles of the FDDS's are shown in FIG. 3. As can be seenin said figure, the release profiles of capsule 1 and 2 (undamagedFDDS's) did not differ significantly from that of capsules 3 and 4(ruptured FDDS's). During the first 4 hours, the release profiles areidentical. After 4 hours a minor difference becomes apparent in that therelease rate of the ruptured FDDS is slightly higher than that of thenon-damaged FDDS's. This difference is however is never more than 8%.

Conclusion/Discussion

The FDDS of the invention is capable of staying afloat even aftermechanical damage and rupture. The damage hardly affects thenicotinamide release profile. Possibly, because of the swelling of thehypromellose upon contact with water, cracks in the wall are effectivelyclosed restoring the integrity of the FDDS.

Example 5: In Vivo Release of Nicotinamide in Healthy Human VolunteersUsing FDDS

Healthy adults, 4 women and 4 men, were recruited as volunteers in atrial to investigate the pharmacokinetic profile of the nicotinamideFDDS of the invention. The trial was performed with 300 and 600 mg FDDSformulations as described in example 3.

During the trial blood was sampled at pre-determined intervals. Samples(Li-heparin) were collected and frozen for storage. In addition urinewas collected (24 h). The entire protocol was as described in table 5.

TABLE 5 Protocol for determining PK profile of Nicotinamide FDDS Startof trial 7:30 Arrival of subjects (empty stomach) at test location.Canule for blood sampling is placed. Blood sample T0 8:00 Subjects havebreakfast (1-2 sandwiches) and drinks (tea, fruit juice) 8:15 Subjectsingest nicotinamide FDDS 8:45 Blood sample T1 9:45 Blood sample T210:45  Blood sample T3 Subjects have drinks (tea, coffee, water and/orjuice) 11:45  Blood sample T4 12:30  Subjects have lunch (3-4sandwiches) and drinks ((tea, coffee, water, and/or juice) 13:00  Bloodsample T5 16:00  Blood sample T6 Subjects have drinks (tea, coffee,water and/or juice) After Subjects go home. Subjects continue to collecttheir urine 16:00  samples. At home the subjects have dinner and drinks(standard) and are told not to take alcohol containing drinks 7:30Arrival of subjects (empty stomach) at test location and hand (next overtheir urine samples. day) 8:00 Blood sample T7 End of trial

The stored Li-heparin samples were analyzed using a standard HPLCmeasurement. Measurements were performed with and without proteinremoval from the plasma, as it appeared that the protein removalnegatively affected resolution of the analyte(s). These problems, whichcould not be resolved instantaneously, did however not prohibit thedetection of the nicotinamide in the various samples. For illustrativepurposes, FIG. 4 is referred to, showing the detection of nicotinamidein the plasma of one of the test subjects. From this figure it can beinferred that the ingestion of the FDDS caused a significant andpersistent increase in the subject's nicotinamide plasma level.

The overall results showed that the FDDS of the invention was capable ofmaintaining an increased nicotinamide plasma levels in vivo for a periodof at least 8 hours after ingestion.

Example 6: Preparation of Floating Drug Delivery System with Levodopaand/or Carbidopa Materials

Levodopa (Ph.Eur.quality), Carbidopa (Ph.Eur.5.8 quality) and HPMC(Hypromellosum 4000 mPa·s., viscosity 2% m/V) were obtained from BufaBV, Uitgeest, The Netherlands). Macrogol 6000 (Polyethylenglycolum 6000)was obtained from Fagron, The Netherlands. Eudragit RL PO (PharmaPolymere, Röhm GmbH) was obtained from Chemische Fabric, Kirschenallee,Darmstadt, Germany.

Methods

A number of different coating dispersions (also referred herein as“suspensions”) were prepared (see Table 6). The required amount of HPMCwas weighted to a beaker and then mixed with Ethanol (100 ml).Subsequently, the active substances were added in the amounts indicatedbelow. In parallel, in another beaker Macrogol 6000 was prepared bymelting at a temperature not higher than 80° C., after melting, ethanol(50 ml) was added and subsequently the required amount of Eudragit RL POwas added. The cooled solution was mixed with the contents of the firstbeaker to provide a coating dispersion.

TABLE 6 composition of the different coating suspensions. IngredientCoating 1 Coating 2 Coating 3 Coating 4 Coating 5 HPMC 4.0 g 4.0 g 5.0 g5.0 g 4.0 g Eudragit RL 3.5 g 3.5 g 3.5 g 3.5 g 3.5 g PO Macrogol 1.0 g1.0 g 1.0 g 1.5 g 1.0 g 6000 levodopa 6.0 g — — 7.0 g 7.0 g carbidopa —0.6 g 0.6 g 0.7 g 0.7 g Ethanol 150 ml 150 ml 150 ml 150 ml 150 ml

Hard gelatin capsules (No. 3) were coated with the different coatingdispersions using an appropriate spray nozzle according to standardprocedures. Briefly, the coating dispersion was sprayed onto the surfaceof the capsules rotating in a small container under a heated air streamuntil the required amount of drug-polymer mixture as determined byweight analysis was sprayed on the capsules.

Dissolution test were performed in a beaker with 500 ml of 0.1 M HCl atpH=1.03-1.09 at a temperature of 34-38° C. while stirring at 150 rpmusing a magnetic stirrer.

Samples (2.5 ml) were taken every 30 minutes up to 7 hours with asyringe. The samples were analysed at 280 nm for the content of activeingredients using a spectrophotometer. When the combination capsuleswere analysed the absorption was assumed to be caused by both thelevodopa and the carbidopa in the same ratio as they were present in theproduct. The assumption that both the drug release and the contributionto the absorption were relative to the presence of both components inthe product can be justified by the fact that the solubility of bothmaterials is within the same order of magnitude and by the fact that thespecific absorption of the materials differs less than 20%.

Results

All gelatin capsules were floating on the stirred 500 ml of 0.1N HCl upto a period of at least 24 hours from the onset of the experiment.

Four capsules were coated with coating suspension 1, and two of themwere subjected to the dissolution test in a beaker with 500 ml of 0.1NHCl. The discussed capsule contained 87.4 mg levodopa which was presentin the polymer coating in a concentration of 41.4%. After six hours,87.38 mg of active substance was released, showing that drug release wascomplete after 6 hours. The capsule was still floating on the 0.1N HClafter 24 hours.

FIG. 5 illustrates the dissolution profiles of a capsule coated withlevodopa in a coating comprising HPMC. Drug release is expressed aspercentage of the theoretical maximum. The figure shows a representativelevodopa release profile obtained with coating suspension 1. Thelevodopa concentration in the simulated gastric fluid graduallyincreases up to 5 hours, after which it remained almost constant.

Coating suspension 2 was used to coat four capsules with carbidopa, andtwo of them were subjected to the dissolution test. The discussedcapsule contained 11.67 mg carbidopa, constituting 6.59 wt % of thecoating composition based on dry weight. After six hours, 10.125 mg ofactive substance was released. FIG. 6 illustrates the dissolutionprofiles of a capsule coated with carbidopa in a coating comprisingdifferent amounts of HPMC (see Table 6). Drug release is expressed aspercentage of the theoretical maximum. FIG. 6 shows a representativecarbidopa release profile obtained with coating 2.

Coating suspension 3 was used to coat another four capsules and two ofthem were subjected to the dissolution test. The discussed capsulecontained 10.50 mg carbidopa, constituting 5.94 wt % of the coatingcomposition based on dry weight. After six hours, 1.14 mg of activesubstance was released. FIG. 6 shows a representative carbidopa releaseprofile obtained with coating 3. The higher quantity of HPMC in coating3 leads to a slower release of active substance. Moreover the releasewas incomplete. This shows that, by varying the polymer content of thecoating composition, the rate of drug release from the floating particlecan be altered.

Next, coating suspensions 4 and 5 comprising a mixture of levodopa andcarbidopa as active ingredients were evaluated.

FIG. 7 illustrates the dissolution profiles of a capsule coated with thecombination of levodopa and carbidopa in a coating comprising differentamounts of HPMC (see Table 6). Drug release is expressed as percentageof the theoretical maximum. The figure shows that the release oflevodopa and carbidopa from a capsule coated with suspension 4 increasessteadily in time. A capsule contained 97.13 mg levodopa and 9.71 mgcarbidopa which were present in the coating at concentrations of 39.55%and 3.95% respectively. In contrast, absorption of carbidopa andlevodopa combination in a market available normal dosage form liketablets is rapid and virtually complete in 2-3 h. Extended-releasetablets absorption is gradual and continuous for 4-8 h, although themajority of the dose is absorbed in 2 to 3 h. FIG. 7 also shows the drugrelease from a capsule coated with suspension 5. The reduced amount ofHPMC in the coating resulted in a somewhat faster release of the drug.

Example 7: Development of a (+/−) 300 mg Levodopa FDDS

Four different floating drug delivery systems are produced in accordancewith this invention, containing Levodopa as the active ingredient:

-   -   Levodopa 1: size 4 capsule coated with a first layer containing        79% levodopa (dry solids weight percentage) and a combination of        hypromellose, in a high hypromellose to starch ratio and a        second layer of said hypromellose starch combination with 0%        levodopa;    -   Levodopa 2: size 4 capsule coated only with a layer containing        79% levodopa (dry solids weight percentage) and a combination of        hypromellose, in a high hypromellose to starch ratio;    -   Levopdopa 3: size 4 capsule coated with a first layer containing        79% levodopa (dry solids weight percentage) and a combination of        hypromellose, in a low hypromellose to starch ratio and a second        layer of said hypromellose starch combination with 0% levodopa;        and    -   Levodopa 4: size 4 capsule coated only with a layer containing        79% levodopa (dry solids weight percentage) and a combination of        hypromellose, in a low hypromellose to starch ratio.

The precise compositions of the FDDSs and the suspensions used forproducing them is given in the following tables.

Levodopa 1 79% Ldopa coating 0% Ldopa coating FDDS suspension FDDSsuspension Levodopa 79%   8 g — — Hypromellose 16% 1.6 g 79% 3.2 gPregelatinized starch  4% 0.4 g 20% 0.8 g Magnesium stearate  1% 0.1 g 1% 0.1 g Aceton —  90 ml —  60 ml Water —  15 ml —   7 ml Capsule sizeSize 4 ‘pressed to lock’ Amount on FDDS corr. to 330 mg of Ldopa 67 mgof coating

Levodopa 2 79% Ldopa coating 0% Ldopa coating FDDS suspension FDDSsuspension Levodopa 79%   8 g — — Hypromellose 16% 1.6 g — —Pregelatinized starch  4% 0.4 g — — Magnesium stearate  1% 0.1 g — —Aceton —  90 ml — — Water —  15 ml — — Capsule size Size 4 ‘pressed tolock’ Amount on FDDS corr. to 330 mg of Ldopa 0 mg of coating

Levodopa 3 79% Ldopa coating 0% Ldopa coating FDDS suspension FDDSsuspension Levodopa 79%   8 g — — Hypromellose  4% 0.4 g — —Pregelatinized starch 16% 1.6 g — — Magnesium stearate  1% 0.1 g — —Aceton —  90 ml — — Water —  15 ml — — Capsule size Size 4 ‘pressed tolock’ Amount on FDDS corr. to 330 mg of Ldopa 0 mg of coating

Levodopa 4 79% Ldopa coating 0% Ldopa coating FDDS suspension FDDSsuspension Levodopa 79%   8 g — — Hypromellose  4% 0.4 g 78%  0.8 gPregelatinized starch 16% 1.6 g 20%  0.2 g Magnesium stearate  1% 0.1 g 2% 0.025 g Aceton —  90 ml —   25 ml Water —  15 ml —    2 ml Capsulesize Size 4 ‘pressed to lock’ Amount on FDDS corr. to 300 mg of Ldopa 15mg of coating

Floating Capacity and Release Profiles

Release profiles of Levodopa from all FDSSs was tested using the USPdissolution system II (paddle method) (Prolabo) with 1 L of 0.01 N HClas the dissolution medium (T=37±1° C.). All FDDSs remained afloat in thedissolution bath during the entire period of testing (12 hours).

In FIG. 8 the release curves of the levodopa 1-4 have been plotted(percentage of the total Ldopa content dissolved vs. time). The figureshows that the release profile of Ldopa can be manipulated precisely. Bychanging the composition of the coating polymers (in this case bychanging the hypromellose to starch ratio) the rate of release of Ldopacan be increased or decreased. The formulations with a higher relativeamount of hypromellose have a lower rate of Ldopa release than theformulations with a higher relative amount of starch. Besides thecomposition of the active ingredient coating layer, the application ofan additional layer of coating (containing no Ldopa) can suitably beapplied to lower the rate of release of Ldopa, as can be derived clearlyfrom the graphs in FIG. 8 (i.e. by comparison of Levodopa 1 and levodopa2 and by comparison of levodopa 3 and levodopa 4).

Effect of Damage and Self-Repair Capacity

The FDDSs were tested for their ability to maintain their floatingcapacity and the release profiles since many floating drug deliverysystems of the prior art are known to be very vulnerable to damageresulting in impairment or total lack of their floating capacity (andhence gastric retention). A common cause for damage is inadvertentchewing movement by the subject taking the FDDS.

The FDDSs Levodopa 1-4 were damaged deliberately by squeezing them in abench-vice, until cracks/ruptures developed visible to the naked eye.The damaged FDDSs were subjected to the same tests as the undamagedFDDS' (as described above)

All damaged FDDSs remained afloat in the dissolution bath during theentire period of testing (12 hours). The release profiles of the damagedand undamaged FDDSs have been plotted in FIG. 9 (9 a: L-dopa 1, 9 b:L-dopa 2; 9 c: L-dopa 3; and 9 d: L-dopa 4). As can be inferred fromthese figures, the effect of damaging on the release profile is onlymarginal. At no time, the difference in released levodopa betweendamaged and undamaged formulation exceeded 8% and it was, in most casesbelow 5%.

To cause damage (cracking/rupture) visible to the naked eye, asignificant force had to be applied, which required the use of the benchvice.

1-18. (canceled)
 19. A floating drug delivery system (FDDS), comprisinga particle having a hollow, gas-filled core bordered by a wall of atleast one polymer selected from the group of aqueous soluble, erodible,disintegrating and degradable polymers, the wall being surrounded by acoating comprising an active ingredient.
 20. The floating drug deliverysystem according to claim 19, wherein the particle is a capsule.
 21. Thefloating drug delivery system according to claim 19, wherein the coatingcomprises a polymer that swells upon contact with water.
 22. Thefloating drug delivery system according to claim 19, wherein the coatingcomprises a combination of HPMC and starch.
 23. The floating drugdelivery system according to claim 19, wherein the coating is selectedfrom the group consisting of coatings resistant to gastric juice,release-controlling coatings, and mixtures thereof.
 24. The floatingdrug delivery system according to claim 23, wherein therelease-controlling coating comprises (a) a swellable, poorlywater-soluble or water-insoluble polymer; (b) one or more entericpolymeric material(s); (c) a mixture of at least two release controllingpolymers; (d) a mixture of an enteric polymer, and a release controllingpolymer.
 25. The floating drug delivery system according claim 19,having a density less than 0.95 g/cm³.
 26. The floating drug deliverysystem according claim 25, having a density less than 0.9 g/cm³.
 27. Thefloating drug delivery system according claim 26, having a density lessthan 0.8 g/cm³.
 28. The floating drug delivery system according claim27, having a density less than 0.7 g/cm³.
 29. The floating drug deliverysystem according to claim 19, which is capable of remaining in thestomach for at least 6 hours and/or of releasing active ingredient tothe stomach and proximal small intestine for at least 6 hours.
 30. Thefloating drug delivery system according to claim 19, wherein the activeingredient is nicotinamide.
 31. A method of treatment or prevention of asymptom or pathology associated with a deficiency in essential aminoacid absorption and/or metabolism, the method comprising administeringdaily to a subject in need thereof <5 separate oral dosage unitscomprising nicotinamide in a total daily dosage of 10-500 mg/kgbodyweight of the subject.
 32. The method according to claim 31, whereinthe symptom or pathology is selected from behavior and/or psychiatricabnormalities, neurological disorders and/or symptomatic disorders. 33.The method according to claim 31, wherein the symptom or pathology isselected from the group consisting of attention deficit hyperactivitydisorder (ADHD); attention deficit disorder (ADD); autism spectrumdisorders; apathy; anxiety; panic attacks; depression;obsessive-compulsive behavior; hostility; hyperirritability; mania;memory loss; delirium; organic dementia; emotional liability; deathwish; unmanageable behavior; contact and play disability; restlessness;chaotic behavior; stress-sensitive fits of crying and temper tantrums;extreme sleeping difficulties; epilepsy; psychomotor retardation;dizziness; bulbary paralysis; tremor; spasm; paresthesia; hyperesthesia;increased tendon reflexes; disorientation; anorexia; glossitis;defecation problems; constipation; dermatitis; atopic eczema;pellagra-like skin disorders; chronic kidney disease and nephrotoxicity.34. The method according to claim 31, wherein the dosage unit comprisesa floating drug delivery system including a particle having a hollow,gas-filled core bordered by a wall of at least one polymer selected fromthe group of aqueous soluble, erodible, disintegrating and degradablepolymers, the wall being surrounded by a coating comprising an activeingredient.
 35. A method for providing a floating drug delivery system(FDDS) according to claim 18, comprising the steps of: (a) providing agas-filled particle, preferably a capsule, made of at least one aqueoussoluble, erodible, disintegrating or degradable polymer; (b) providing acoating dispersion comprising active ingredient, a polymer, optionallyadditive(s), in a volatile solvent; (c) applying at least one layer ofdispersion on the surface of particle; and (d) allowing the evaporationof the volatile solvent such that a layer comprising the activeingredient is formed at the surface of the particle.
 36. A method ofdiagnosing a deficiency in essential amino acid adsorption and/ormetabolism in a subject, the method comprising determining the urinaryexcretion of one or more indoles from the subject.
 37. The method ofclaim 36, wherein the indole is an indican.